KICK START BEVEL DRIVE

The bevel gear is the output from the kick start unit and meshes with the gearbox to provide drive to the crank shaft during starting.  It is housed in the kick start outer cover  (at the top of the picture)
The kick start bevel gear is in constant mesh with the clutch and crank bevel gears and so is rotating all the time the engine is running.  With the engine stationary the kick start  leaver brings the quadrant into contact with the quadrant drive gear which in turn rotates the kick start bevel and thus the engine.  If the kick start leaver is held down with the engine running the ratchet comes into play.  With the lever released the quadrant returns to it's parked position out of mesh with the quadrant gear and the bevel gear rotates freely.

PARTS

1   The kick start outer cover
2    "O" seal  (fitted on cover)
3   The bevel gear and shaft
4   Washer (not shown, I forgot to take to out of the casting)
5   Cir clip
6   Spring

7   Quadrant drive gear  - note the three ratchet teeth, earlier   models had six.

8   Quadrant gear
  

9   Bevel gear Cover plate and bearing

The bevel gear and shaft have and oil return spiral cut into the bearing surface in order to minimise oil escaping from the gearbox.
I'm not sure if the gear box oil level reaches this high or if the gear is lubricated by splash alone. Any oil that finds it's way along this bearing will eventually get onto the quadrant and the kick start shaft.  Since the kick start shaft has no means of preventing oil escaping  this is what I may have been experiencing. However I favor my problem being caused but the damaged "O" seal and possibly over filling.  We shall see.

The Service Book says if the bevel gear is meshed too tightly with the clutch bevel it can produce a whine when the engine is running in neutral.  Backlash is provided by fitting paper gaskets between the unit cover and the gearbox casting.  I note that mine had two gaskets fitted, apparently you check the slack through the oil filler hole.

Now for the new shaft and putting it all together again.